1. Field of the Invention
The invention relates to clutches and particularly to clutches which are operated automatically by centrifugal force at a predetermined speed of rotation so as to connect an inner drive rotor assembly to an outer driven member or load. More particularly, the invention relates to an improved mounting arrangement for the centrifugally actuated clutch shoes which absorb the forces heretofore exerted directly on the mounting components, and in addition provide a smooth, low-friction sliding surface between the pivot pin and its mounting components.
2. Description of the Prior Art
There are numerous types and arrangements of centrifugal clutch constructions in which one or more clutch shoes are retained in retracted position by springs until sufficient centrifugal force acts on the shoes to overcome the force of the retaining springs, whereupon the clutch shoes pivot and swing outwardly and engage a stationary clutch housing or drum.
Some of these clutch constructions have a pair of arcuate-shaped clutch shoes which are pivotally mounted in an end-to-end relationship with respect to each other by a pair of pivot pins on a backing plate member. The backing plate, in turn, is fixed to a drive shaft or hub for rotation with the drive shaft.
These pivot pins use a simple beam-type mounting arrangement for the clutch shoes, wherein the pivot pin is supported on both ends by the backing plate and an axially spaced drive flange. The pivot pins extend through axially aligned openings formed in the backing plate and drive flange, and through openings formed in the clutch shoes for pivotally mounting the shoe between the backing plate and drive flange.
Problems have occurred in these types of constructions in that considerable forces are exerted directly on the shoes upon the shoes couplingly engaging the driven member. These forces are transmitted through the pivot pins to the backing plate and drive flange. Occasionally, the drive flange will develop cracks or fractures in the metal which surrounds and defines the pivot pin receiving openings. These flanges preferably have as minimal an amount of metal as possible at their outer ends in which the pivot pin openings are formed in order to reduce the weight of the clutch. Either the flange thickness or the amount of flange metal surrounding the pivot pin receiving openings must be increased to prevent this fracturing, thereby undesirably increasing the weight of the clutch. The main problem occurring with these prior constructions is wear. Notches and grooves are worn in the pin, shoe and/or mounting flange, resulting in improper operation or non-function because of resulting clearance problems.
Some clutch constructions use a shock-absorbing bushing that is telescopically mounted on and extends throughout the length of the pivot pin to eliminate this fracturing problem. However, this bushing requires a greater diameter opening to be formed in the clutch shoe through which the pivot pin and surrounding shock-absorbing bushing extend, thereby requiring additional metal and weight in the clutch shoe than would be required if the resilient bushing were not used.
There is no known centrifugal clutch construction of which I am aware which provides for pivotally mounting the clutch shoes on a simple beam-type pivot pin mounting arrangement in which the ends of each pivot pin are telescopically mounted in shock-absorbing bushings which, in turn, are telescopically mounted in openings formed in an axially spaced backing plate and drive flange, and in which the clutch shoe is mounted directly on the pivot pin without any intervening bushing material, thereby reducing the size of the pivot pin receiving opening formed in the clutch shoe.